You could collect rain water, the water from your creek or spring, or elsewhere and filter it. Storage is pretty simple, really. Keep it somewhere cool, and label it so you know the storage life. Typically one year is the max for airtight water storage, but you could ask others here about longer storage. You can purchase 50 gal. drum containers for large storage, and the internet has numerous places to find those I am sure. You could also buy a water filter unit and spare filters. For smaller emergency kits, you can buy pre-packaged water that come in handy space age packets, great for autos and emergency kits. For backpacking and hiking, as a mobile solution, you could buy a pump filter that costs around $100-250 for a really decent one. There are treatment kits available for water (most come with instructions), purification tabs, and in a pinch you could always boil water for five minutes or use a sparingly tiny (a drop or two) amount of bleach per batch -although I don't know how much exactly and I wouldn't try it unless desperate. You could also try studying some survival guides, some are floating around the Monkey household -these survival techniques may come in handy and will help you to utilize water in the wilderness safely.

Besides that, I am not too sure what else you may require.

"It is no measure of health to be well adjusted to a profoundly sick society. "-- J. Krishnamurti“The further a society drifts from truth the more it will hate those who speak it.” -- George Orwell

subzero, if you get more than 30" of rain per year at your location you have more than enough water to keep you going in everything but a long drought depending on your usage. A simple pump hooked up to a few 1500 gallon tanks and you've got enough pressure to make your house seem like city/county/whatever water is still hooked up.

If your enemy is secure at all points, be prepared for him. If he is in superior strength, evade him. If your opponent is temperamental, seek to irritate him. Pretend to be weak, that he may grow arrogant. If he is taking his ease, give him no rest. If his forces are united, separate them. If sovereign and subject are in accord, put division between them. Attack him where he is unprepared, appear where you are not expected. - Sun Tzu, The Art of War

In any sort of a long run, food or water storage is only a short term situation. I have a flood control dam about 500 feet from the house, a shallow well and a deep well and downspouts from the roof. I don't know what will work, but I darn well don't want to be thirsty. I think filters and chlorine are good ideas and I have a few pounds of swiming pool cholorine that is solid and good for long term storage. That said we keep about 50 gallons of spring water in stock and rotate it as we use it. It just tastes a lot better than our water. As far as the toliets and such, we have a shallow well pump and a deep well pump, both electric and a shallow well hand pump. We have been without electricity for 10 days and never had to worry about water. We did fill the tub and buckets when we ran the generator to flush when that wasn't running. I personally think that water is to important to store for more than short term use. I don't know what you would do in an urban area, except probably die or leave.